It's already billions of dollars and thousands dead. That is sufficient to be against my interests, which are peace and prosperity, and anyone who supported Trump because of his fairly consistent position of being against these conflicts is right to be pissed.
I don't see it as much more complex than this:
Them: Give us billions of dollars to kill a bunch of people on the other side of the planet.
Us: Why?
Them: You'll just have to see how it works out.
Us: Fuck you. No.
It seems to me that you're putting the burden of proof entirely in the wrong place. The people intending to take your money and use it to kill people are the ones who need to justify their actions, all the more so when they have previously said acting in that way is dumb and wasteful. Opposing them should be the default position.
